Abstract Several experimental groups observed temporary modulations of some nuclei strong and weak decay constants, which are of the order of 10−3 and with periods of one year, solar day, i.e. 24 hours and some others. In our experiments the decay rates were measured for 55Fe e-capture and 60Co β-decay during 2012–2020. Altogether, six decay rate dips of the order 10−2 – 10−3 and with duration from 40 to 208 hours were found, they deviate essentially from exponential decay rate fit. It is shown that their occurrence correlate with x-ray solar flares with significant reliability. Besides, two long term deviations of 55Fe decay rate of 62 and 41 days were observed in 2017–2018, it’s argued that they are related to the change of 11 year solar cycle stages.