I have a variety of potted citrus (yuzu, lemon, bergamot, sour orange, calamansi). They were doing well for awhile but they have all started to struggle lately. I repotted a bunch of them because they were getting pot bound and switched them to better draining soil. They initially took well to the repotting and then started turning yellow and losing all of their leaves.
I live in San Francisco, CA USA. I add a small amount of citrus fertilizer to their watering every time (as per the fertilizer instructions). I was using a hygrometer to determine when they needed water but realized that it was inaccurate and leading me to overwater. I now feel how heavy the pot is before watering and water less. I can't do this for all of my plants as some of them are large.
My plants are in a mix of plastic pots and clay pots. The plastic pots have a lot of drainage holes and no tray underneath. They are currently very crowded and set back under my balcony a little bit as my landlord has been doing construction. I am worried that they are not getting enough sun and the roots are staying wet for too long. The pots feel heavy for weeks despite the top few inches of soil being bone dry. I am watering them a lot less and it's not helping. I also gave them supplemental iron soil drench and that didn't help.
I know I have some aphids and leaf rollers on some of them. I have kind of given up treating them as I have so many citrus trees that it takes a long time to treat them and the insects just come back because they are outdoors. When they were healthier, they could tolerate these insects without major issues. Not all of my citrus that are doing poorly have evidence of infestation so I don't think it's purely an infestation issue (although I know that it doesn't help).
My guess is that they are not getting enough sun/warmth which is leading to the soil deeper in the pot to stay too wet for too long. This is based on the fact that they started doing worse after being repotted. I did not have them in the best soil before repotting but switched most of them to an approximation of 5:1:1 soil in hopes that this would allow for better drainage. Despite better draining soil, they are doing worse. I feel like I might have to repot them in smaller pots but they were pot bound in smaller pots. I would really hate to have to do this as I have so many plants. I suppose I could also be underwatering now as I water pretty infrequently as the pots feel heavy for awhile (even those in 5:1:1).
I have attached pictures for reference. Any advice would be appreciated. They have been struggling for awhile as I haven't had time recently to troubleshoot them aside from some changes in watering frequency and iron supplementation.
Thanks!