How recently was it given guano?
What did you use for magnesium?
When was the last time it got calcium?
Watering schedule?
TBH it looks fried.
Looks like it was originally lacking a little calcium. Adding magnesium has just amplified the need for calcium.
If you added guano too, its just made it worse.
Calcium deficiency starts out, as the plant just being a little "pale". Then brown spots, like you have start appearing.
Adding more of what it doesn't need. Just means it has less of what the plant requires. It antagonizes symptoms further.
Do you ph the water?
Whats the ph of your soil?
Need info please.