Possible reaction to indian almond leaves?

It it possible for an axolotl to have some kind of reaction to indian almond leaves? Either an allergy or some kind of irritation?

My male leucistic was scratchnig at his gills a few days ago, and knowing that the summer temps can precipitate fungus I added an indian almond leaf to his tank. Today when I got home from work he looked a bit flushed, I didn't think much of it until I had a chance to observe properly later this evening, but it looks like badly irritated skin much like ammonia burn.

So I tested the water (ammonia = 0 nitrite=0 nitrate=25) and figured the only thing that had changed was the addition of the leaf.

We've done a 90% water change (no fun at 10pm ) and he seems OK other than the redness. He's busy scoffing pellets and flapping his gills as normal now, but he's still red and a little veiny.

His tank mate seems unaffected, although obviously redness isn't easy to see in a black wildtype, but they have both been fidgety for the last couple of days.

Irritation - definitely. Cause? Either a reaction to the indian almond leaf, or maybe a bad leaf?

Any input gratefully recieved.

Did you rinse the leaf before adding it to the tank?

I've also read that when adding almond leaves to a tank it can take up to three days to leach enough tannins to become effective. If he had irritated skin prior to you adding the leaf, perhaps the irritation could be a progression of the initial cause?

Yes, I washed the leaf, and it was in there for 4 days.
He'a looking much better this morning, almost back to normal colour.

Maby a chance that pesticide or another chemical was leached into the leaf that couldn't be washed off but leached back out while soaking in the tank just a thought