50% peat does seem high. It depends on the size of the pine bark chips to open it up, and if it is coir peat or bog peat. 50% peat might be ok over summer in the mediterranean nursery, or in heated tunnel production. It might be too much over winter in different situations. I would contact the nursery and find out what other ammendments are in the 50peat/50 bark mix, such as lime or dolomite to balance the pH or do a pH test of your new mix, it may be too acidic with high peat levels.
( other possible additions are iron sulphate, trace element mix, gypsum, etc)
Is the root ball dry ? Perhaps the outer pot mix is wet but the rootball dry. This can happen if the original plug is higher than the rest, or if the original plug was slightly dry and now repels moisture.

People grow citruses successfully in 100% soil dug in their garden and they're doing just great. That's what moisture meters are for, or the fingers. I'm not having too much problems with my medium. When I water, I water thoroughly - 1l of water for a 21cm diameter pot. My soil is my least concern.
Anyways, I'm more interested in my newly set fruit growth speed.

The key to container citrus is having a mix that works well for you. If you have healthy trees that you are happy with in your mix, I wouldn't alter it on my advice, or of any one else.