Advice Needed - Salvia Problem - Yellow Leaves & Spotted Flowers

I have two Slavias growing in clay pots, about years old. They were fertilised with Growchar 2 months ago and have now started to appear sick. Last year I fertilised them with Growchar they were happy all summer long. The overall deep green colour from spring has turned into a yellow-ish one and the leaves are turning yellow from the bottom of the plant and dropping. One of them has red veins on the yellow leaves, the other one is just yellow. I thought it might be a nutritional deficiency a fed them a "slow-release source of primary macro nutrients (NPK 3:2:3)" two days ago. Today they developed spots on the flowers. Can somebody please advise me on what is wrong with them and what else I can do to save them?
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Possibly overwatering or not enough sun are my guesses, but hopefully a salvia expert can help.
Clay pots dry out extremely quickly the water soaks into them leaving the compost dry, so be vigilant with the watering, check every day.
I didn’t know about liking dry, it’s usually forever raining here, and my soil is very rich.
Now the only difference this year is the location - they are standing on a south-facing decking which has 3 walls. So one of them has direct sun almost all day, 8am to 4pm. The other one is under a tree and gets sun 1pm - 6pm. My understanding is they need at least 6 hours direct sun a day and it was rather cloudy here all June. So I'm not sure why the sun would be an issue. My neighbors have the same Salvia in a similar position and it looks happy.
I'm thankful for any further advice. Maybe replanting into larger pots? Could it be a disease? The apple tree and a prunus next to them both have leaf blotch. I'm hesitant planting them out as there is a fungal issue going on in our soil attacking woody plants that I'm trying to fight off.
Sorry for the mess in the corner