New tank...new albino bristlenose pleco...not well

[maggie.bf]

Hi All,
My husbands albino bristlenose pleco started turning red, from his 'nose' onto his 'tummy'. It's a still rather new tank (started 30th Dec 2020). My husband bought the pleco (Geoffrey) two weeks ago. All was fine until yesterday. My son has a mature tank and his pleco is absolutely fine. I tired to attach few photos. It looks like Geoffrey scraped his 'tummy', but I'm not sure if that's the case.
I would be grateful for any advice.

 

[charliebankston]

Is his behavior different? What kind of food is going in the tank?

 

[maggie.bf]

Hi,
Thank you for replying.
We were told not to feed the pleco as there should be enough algea. But so far he had waffle for bottom feeders about 10 days ago. Otherwise pleco will pick up any food that sunk. I don't think the behaviour changed. He lives with 4 danios and 3 guppies in 34L tank.

 

[charliebankston]

If his behavior is same, by that I mean, not acting sick, then it could be food causing color change. Is any of the food labeled color enhancing?