haveing negative rp for some reason

Just got some rp and went to buy some skins already got 2 lulu poolparty and battle boss blitz and after a quick break i did i somehow got -541 rp even though when i bought the lulu skin thats 1350 and had like more then 2000 i still got negative rp hopeing this dosent have problems for my future purcheases and hopeing if there is a solucion