Bryant RedHawk wrote:How much water are you putting on them and how often?
What did the previous owner use on the "lawn" poison wise and fertilizer wise?
Where did the compost you used come from, how was it made?
Usually yellowing leaves are caused by lack of mineral balance, magnesium and manganese along with iron defect are some of the usual reasons for yellowing leaves.
Blue berries like acidic soil, if they aren't doing well, pH would be the first thing to check and adjust if needed.
Bryant RedHawk wrote:1), sounds like you probably are over watering if they are planted in the ground, if they are in containers, you want to make sure you have a straw pushed in to the bottom of the container and use a "dip stick" to check moisture, not your finger, it can't reach down deep enough for a good reading.
2) poisons can last over 10 years in the soil. fungi are your best friend to remediate suspect soil (if there is grass, the soil is suspect).
3) store bought compost has become notorious for being contaminated (if the bag doesn't say "Organic" don't bother buying it), it didn't use to be that way but now it is.
Apple trees do not like acidic soil, some where between 6.5 and 7.2 can be considered perfect for apples, peaches, plums, pears, figs, cherries and most other fruit trees.
Blue berries want pH to be close to 5.5
Best amendment for blue berries is sulfur, peat works fair if it is worked into the soil prior to planting.
Basic is anything higher than 7.2 acidic is anything lower than 7.0 (neutral)
hope that helps you out.