You may to evaluate firstly what is the student´s learning level using the Biggs scale: pre-structural, monostructural, multistructural or relational. Second, you must to define your learning objectives according to your findings. Third, you must to establish a gap among the measured level and your objectives. Finally, you can to search what type of verbs manages appropiately and it reveals the adquisition of higher levels of learning.
Be mindful that symptoms may not tell the whole story, so you may want to ensure that you do a lot of formative assessments to identify where the learning gaps are before doing your summative assessments. In this way, you catch the "slowness" earlier rather than later and do any necessary interventions to address it.
When the learning is slow it can be multifactoriel. You need to adapt the teaching to find the one ou two most important factors. You can do evaluation at multiple key moment of the learning. Also it is always better to motivate the students. Find the motivation and adapt the teaching method even partially.