Unfortunately sebae anemones are commonly sold as "White with colored tips", but anemones aren't naturally white in nature. They've become bleached at some point in the collection and shipping process. I've been to saltwater wholesale warehouses with troughs full of "white with colored tips" sebae anemones and it's quite sad. I imagine they're normally a beige or tan color.
I've been nursing a purple one back to health for a couple months now. I bought two, tried to treat one with cipro unsuccessfully and the other I left in a tupperware container with sand and rubble and an egg crate lid on top to keep it from floating out. Seems like they easily roll onto their fronts with their foot exposed (like in your first photo) when they are unhappy.
I'm not sure yours is sick right now, or just in poor shape. It may not require cipro treatment like a magnifica anemone would when it's showing signs of distress. If the mouth is completely gaping and it's deflating regularly then treat it. If the mouth is closed or only slightly open and the anemone stays inflated then you just need to slowly acclimate it back to light IMO. From what I've experienced so far with my sebae, you just need to keep it in one place and slowly slowly move it from a low light area to higher light to bring it back to health without shocking it. Keep decent flow on it to help with gas and nutrient exchange. I saw mine expose zooxanthellae regularly in the afternoons during the acclimation process as the zoox produced faster than it could process them. IMO this is not signs for alarm. I hypothesize that when the anemone is bleached and its health is compromised, it can't process zoox production as quickly as when it's fully healthy. It became so accustomed to little/no zoox production when bleached that the sudden increase in zoox population from light in the tank is more than it can currently handle. It will eject whatever excess it can't handle in the form of little brown stringy globs of zoox. A strategy of balancing it's internal population of zoox when it's not used to it. This is just my theory at the moment at least.