Strawberry Guava Sickness Red leaves

[luvshelio]

My strawberry guava is in a 10 gal and recently has been dropping leaves in a seemingly random order after they turn red. I suspect some type of fungal disease, and I really don’t know what to do as the plants new growth just turns black and it’s quickly losing its old leaves. Please help me identify the issue and find the solution!

 

[cpp gardener]

Honestly, it doesn't look that bad. They frequently drop lots of old leaves slightly before and during spurts of new growth.
What is your watering process (frequency, thoroughness) and fertilizing program?
How much sun does it get?
How cold did you get this winter?

 

[luvshelio]

Well we’ve been getting a lot of rain latley and so I haven’t been watering it and I put slow release fertilizer spikes in 2 weeks ago when it was spring. It also hasn’t been so cold that I think it would get sick or anything. We’re in zone 10. If it is getting a growth spurt, I’m confused as to why all the new growth starts to die and turn black?

 

[cpp gardener]

It’s probably from the hard frosts during the winter rather than the current weather. It will probably continue for a few weeks and then the leaves will stop dropping.