Newly planted yew hedge issue

Markb24

I planted a yew hedge in December of 2019. All rootball hedging. I have noticed within the last week that we have some brown patches at the end of some branches. The browning can be at the top middle or bottom of the trees so it seems very random and below the browning seems perfectly healthy growth. The trees themselves also look perfectly healthy.  

The ground was prepared with the finest screened topsoil I could find and mushroom compost mixed with the soil around the footballs at a rate of around 25-30%. 

I have been checking regularly and have only watered 3 times since planting due to the amount of rain we have had over the past few months. 

The browning is really concerning as I don not want it to spread and affect the trees any further than it already has, if I can. 

Some images are attached, I may be worrying about nothing but any advice would be appreciated. 

I have also been reading online they may benefit from a foliage feed could anyone recommend what type of feed would work best, when and how often to use. 

Markb24

Markb24

Markb24

Borderline

The plants should really be planted a bit more spaced out and at least a foot from the fence. They may struggle to get water into their root area. Browning bits are not too bad. You will just need to trim the shrub back anyway, so cut them out. 

Long term, shrubs benefit from a thick layer of bark chip mulch to seal in moisture. However, keep an eye on watering during the warmer months for the first 2-3 years. The roots need time to settle into the surrounding soil. I don’t recommend any feeding, but others may have a different view.

Fairygirl

I'd agree that they may have got a bit dry due to their proximity to the fence, and heavy rainfall tends to give the impression that they don't need watered, but it's often not the case. 
They're easy to keep tightly trimmed though for hedging, but it would have been better if they'd a little more room. However, it's perfectly salvageable with some care. Yew is very tough

As @Borderline says, trim those little bits off, they're nothing to worry about, and be vigilant with watering. Add a mulch, and bear in mind that wind is very drying too, so lookout for the ground being dry if you get any windy, but dry spells.
If the soil is reasonably hearty, they shouldn't really need food, but you can add a sprinkle of B,F&B if you have it, and tickle it in before watering and mulching. The ground looks a bit solid, so it would be worth just lightly breaking it up with a trowel first.
 
Liquid seaweed is good as a foliar feed, or just as a general feed for foliage plants, but not vital. You can do that later in the year if it looks like it needs a pick me up, but do it on a cloudy day, if you do a foliar feed. 

Markb24

They were planted at 55cm centres this was the recommendation of the nursery where I purchased, although I did say I wanted them as close as possible. I will definitely try some fish, blood and bone and also the liquid seaweed. 

I was intending to mulch With bark this month but with what is currently going on in the world getting mulch is proving to be difficult. 

How often should I be watering ? I was thinking on once a week until summer and twice per week in the summer months assuming it’s warmer weather