You should have a doctor watching over you if you're taking such strong diuretics. This can cause a serious electrolyte imbalance and possible kidney damage if things are not monitored closely via periodic blood work. And yes, they are intended to be taken together - separately can cause additional problems to whatever you're already trying to resolve.
I already stop taking spironolactone 25 mg. Now only take Furosemide 40 mg once a day. Does Furosemide 40 mg can cause kidney damage?